Answer
The results of this survey contradict the stated belief because $640\gtμ_X+2σ_X$
Work Step by Step
Let's find the standard deviation:
$σ_X=\sqrt {np(1-p)}=\sqrt {1200\times0.5\times(1-0.5)}=\sqrt {1200\times0.5\times0.5}=17.32$
$μ_X-2σ_X=600-2\times17.32=565.36$
$μ_X+2σ_X=600+2\times17.32=634.64$
Assuming n = 1200 and p = 0.5 (population is equally split) we have a probability of 95% that the result is between 565.36 and 634.64 adult Americans who believe that the amount of tax they pay is too high. So, the results of this survey contradict the stated belief.
